The present invention relates to the field of cathode ray tube manufacture, More specifically, the present invention relates to the fields of applying and testing an anti-reflective film over the viewing surface of a cathode ray tube during manufacture of the tube. The present invention provides an improved method and device for selectively grounding the solder electrodes of the anti-reflective film so that the film and electrodes can be properly tested during production.
Cathode ray tubes (xe2x80x9cCRTsxe2x80x9d) are used in most television sets and computer and video monitors. A typical CRT is illustrated in FIG. 1. The CRT (100) is a glass tube with a bottle-like shape in which a relatively flat bottom portion (101) narrows into an elongated neck portion (102). The relatively flat portion (101) of the CRT (100) is the viewing surface and becomes the screen on which the display of the television set or monitor is generated when the CRT is incorporated therein.
An electro-luminescent material, such as phosphorus, that emits light when struck by an electron beam, is coated over the interior of the screen portion (101) of the CRT (100). An electron gun is then installed in the neck (102) of the CRT (100). A stream of electrons emitted from the electron gun is scanned over the electro-luminescent layer and turned on and off during the scanning to cause the electro-luminescent layer to glow in certain places and not others. In very simple terms, this is how an image is generated on the screen of a television or video monitor.
A yoke (not shown) is provided around the neck (102) of the CRT (100). This yoke produces a changing magnetic field through which the electron beam from the electron gun passes. The electron beam is deflected by the magnetic field of the yoke. Consequently, by varying the magnetic field created by the yoke in a precise cycle, the electron beam can be scanned, line-by-line, over the entire surface of the screen to generate video images thereon.
A cathode ray tube is generally constructed in the following matter. The neck (102) or funnel portion of the CRT (100) is formed open at both ends. Then the relatively flat bottom, or display portion (101) is sealed to the large end of the funnel and the electron gun is installed in the narrow end or neck of the funnel.
The display portion (101) is sealed to the funnel (102) using frit. Frit is a glass paste that can be cured or hardened. Frit, in paste form, is applied around the large end of the funnel (102) between the funnel (102) and the display portion (101). The frit is then cured or hardened to form a frit seal between the funnel (102) and the display portion (101).
After the frit is sealed, the tube (100) is evacuated and a strong vacuum is maintained inside the tube (100) throughout its life. Because of the strong vacuum inside the tube (100), there is a minimal risk that the tube (100) could implode. This risk is, of course, heightened if the tube (100) is damaged or mishandled. In the event of an implosion, a major concern would be flying glass shrapnel produced by the implosion.
To minimize the risk of both an implosion and a resulting spray of shrapnel, a metal band (103) is wrapped around the cathode ray tube (100) over the frit seal. This band (103) is called a reinforcement or heat-shrinkage (xe2x80x9cHSxe2x80x9d) band.
An anti-reflective film (104) is also applied over the viewing surface of the screen portion (101). This anti-reflective film (104) minimizes the reflection of external light from the screen (101) of the cathode ray tube (100). Such reflection degrades the quality of the image that can be displayed on the screen (101) of the tube (100).
The anti-reflective film (104) is in electrical contact with solder electrodes (105) that are formed on the film (104). During the operation of the cathode ray tube (100) as a television or video monitor, the anti-reflective film (104) is electrically grounded through the solder electrodes (105). This grounding prevents a build-up of an electric charge on the anti-reflective film (104). Such an accumulated charge can damage the anti-reflective film (104).
The solder electrodes (105) are electrically connected to the HS band (103) by a piece of conductive tape (106), as shown in FIG. 1. This conductive tape (106) provides an electrical path from the solder electrode (105) into the HS band (103) for purposes of grounding the anti-reflective film (104) of the surface of the screen (101).
During manufacturing and testing of the cathode ray tube (100), it is necessary to test the anti-reflective film (104) and the resistance of the solder electrodes (105) provided on the film (104). In order to complete this testing, particularly the resistance of the solder electrodes (105), the conductive tape (106) must be removed so that the testing equipment can be used to test the resistance of the solder electrodes (105). The tape (106) is then replaced so that the anti-reflective film (104) can be tested. During testing of the anti-reflective film (104), it is necessary that the tape (106) be in place to prevent accumulated charge from damaging the anti-reflective film (104).
This entire process is repeated several times over a period of several days to ensure the quality of the solder electrodes (105) and the anti-reflective film (104). Unfortunately, the repeated removal and replacement of the conductive tape (106) can cause damage to the solder electrodes (105). Moreover, the more often the tape (106) is removed and replaced, the less well it adheres to the solder electrode (105). Consequently, during or after the testing, the tape (106) may no longer make a sufficient contact with the solder electrode (105) to effectively ground the anti-reflective film (104) thereby protecting the film (104) from damage due to accumulated electrical charge.
Consequently, there is a need in the art for an improved method and device for grounding the anti-reflective film and solder electrodes of a cathode ray tube during testing of the film and electrodes. Moreover, this improved means for grounding the anti-reflective film should be adapted for ready and easy removal and replacement as needed without the possibility of damaging or degrading the solder electrodes and other tube components.
The present invention meets the above-described needs and others. Specifically, the present invention provides an improved method and device for grounding the anti-reflective film and solder electrodes of a cathode ray tube during testing of the film and electrodes. Moreover, this improved means of grounding the anti-reflective film is adapted for ready and easy removal and replacement as needed without the possibility of damaging or degrading the solder electrodes and other tube components.
Additional advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The advantages of the invention may be achieved through the means recited in the attached claims.
The present invention may be embodied and described as a device for selectively creating an electrical grounding path between an electrode of an anti-reflective film and a reinforcement band on a cathode ray tube. The device preferably includes a conductive strip that is sized and shaped to make electrical contact with an electrode of the anti-reflective film and the reinforcement band on a cathode ray tube so as to create an electrical grounding path between the electrode and the reinforcement band on the cathode ray tube; and a magnet for holding the conductive strip in place against the reinforcement band. The magnet is attracted to the metallic reinforcement band so as to hold the conductive strip in place.
In one preferred embodiment, the conductive strip and magnet are separate pieces. In an alternative preferred embodiment, the conductive strip and the magnet are integrated as a single unit.
The conductive strip may be formed of a flexible or rigid conductive material. Two preferred materials are silver and tungsten.
The present invention also encompasses the methods of making and using the device described above. Specifically, the present invention includes a method of testing electrodes of an anti-reflective film on a cathode ray tube and other components of the cathode ray tube by (1) creating a grounding electrical connection between an electrode of the anti-reflective film and a reinforcement band of the cathode ray tube with a conductive strip in electrical contact with both the electrode and the reinforcement band; and (2) holding the conductive strip in place with a magnet.
The method continues by selectively removing the conductive strip from the cathode ray tube by withdrawing the magnet. Following removal of the conductive strip, the method continues with testing the resistance of the electrode. Then, the method includes replacing the conductive strip in electrical contact with both the electrode and the reinforcement band; and holding the conductive strip in place with the magnet. At this point, the method can further include electrically testing other components of the cathode ray tube.
The benefit of this method of the present invention is that the conductive strip can be removed and replaced any number of times without potentially damaging the electrode on the anti-reflective film. Thus, the method of the present invention can further include again removing the conductive strip from the cathode ray tube by withdrawing the magnet; again testing a resistance of the electrode following removal of the conductive strip; again replacing the conductive strip in electrical contact with both the electrode and the reinforcement band; and holding the conductive strip in place with the magnet.
In forming the device of the present invention, the method may include integrally forming the conductive strip and the magnet as a single unit. As mentioned above, the conductive strip can be rigid or flexible and formed from any conductive material, preferably silver or tungsten.